Ice nucleating particles (INP)
in the atmosphereby
Heike Wex
from Leipzig, Germany

wex@tropos.deoverview- general introduction- basic knowledge- result from recent field studies

each roughly 1/3 of the talkALL will need to stay on the surface

Heike Wex, 16.3.2022, Virtual lecture series-Cloud and Precipitation Physics and Dynamics

1

atmospheric aerosol particle sources

general introduction

primary: particles are emitted directly
secondary: particulate mass formed from gaseous precursors
particle ageing
particle concentrations: roughly 100 to 10 000 cm-3

INP (ice nucleating particles): VERY rare subgroup, with someten to hundred L-1 or m-3

Heike Wex, 16.3.2022, Virtual lecture series-Cloud and Precipitation Physics and Dynamics

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general introduction

homogeneous freezing- below 0°C, ice is the thermodynamic stablephase, BUT:
- for ice formation, energy barrier needs to be
overcome- ice germ: needs a critical size (rn*), once this isreached, droplet freezes- rn* is temperature dependent

~r2

~r3

Heike Wex, 16.3.2022, Virtual lecture series-Cloud and Precipitation Physics and Dynamics

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general introduction

homogeneous freezing
look out for a good additional explanation in lecture from Thomas Koop on:
https://iac.ethz.ch/group/atmospheric-physics/research/ice-nucleation-colloquium.html- below 0°C, ice is the thermodynamic stablephase, BUT:
- for ice formation, energy barrier needs to be
overcome- ice germ: needs a critical size (rn*), once this isreached, droplet freezes- rn* is temperature dependent- homogeneous freezing: below -38°C,
critical germ size can randomly be reached- above -38°C: INP „stabilize“ or „arrange“
water molecules and fill part of the void
Heike Wex, 16.3.2022, Virtual lecture series-Cloud and Precipitation Physics and Dynamics

4general introduction

heterogeneous freezing
heterogenous freezing, i.e., nucleation is aided by a „catalyst“(a surface on which water molecules can arrange in an ice like manner)
different heterogenous freezing processes:- deposition ice nucleation- contact freezing
T<0°C- condensation freezing
T>0°C- immersion freezing

Heike Wex, 16.3.2022, Virtual lecture series-Cloud and Precipitation Physics and Dynamics

5general introduction

heterogeneous freezing
heterogenous freezing, i.e., nucleation is aided by a „catalyst“(a surface on which water molecules can arrange in an ice like manner)
different heterogenous freezing processes:- deposition ice nucleation (instead condensation & freezing in pores, Marcolli, 2014)- contact freezing
T<0°C- condensation freezing
T>0°C- immersion freezing

Heike Wex, 16.3.2022, Virtual lecture series-Cloud and Precipitation Physics and Dynamics

5general introduction

heterogeneous freezing
heterogenous freezing, i.e., nucleation is aided by a „catalyst“(a surface on which water molecules can arrange in an ice like manner)
different heterogenous freezing processes:- deposition ice nucleation (instead condensation & freezing in pores, Marcolli, 2014)- contact freezing (Hoffmann et al., 2013, BUT: in atmosphere, collisions too seldom)
T<0°C- condensation freezing
T>0°C- immersion freezing

Heike Wex, 16.3.2022, Virtual lecture series-Cloud and Precipitation Physics and Dynamics

5general introduction

heterogeneous freezing
heterogenous freezing, i.e., nucleation is aided by a „catalyst“(a surface on which water molecules can arrange in an ice like manner)
different heterogenous freezing processes:- deposition ice nucleation (instead condensation & freezing in pores, Marcolli, 2014)- contact freezing (Hoffmann et al., 2013, BUT: in atmosphere, collisions too seldom)- condensation freezing (immersion freezing in concentrated solutions, Wex et al., 2014)
T>0°C- immersion freezing

Heike Wex, 16.3.2022, Virtual lecture series-Cloud and Precipitation Physics and Dynamics

5general introduction

heterogeneous freezing
heterogenous freezing, i.e., nucleation is aided by a „catalyst“(a surface on which water molecules can arrange in an ice like manner)
different heterogenous freezing processes:- deposition ice nucleation (instead condensation & freezing in pores, Marcolli, 2014)- contact freezing (Hoffmann et al., 2013, BUT: in atmosphere, collisions too seldom)- condensation freezing (immersion freezing in concentrated solutions, Wex et al., 2014)- immersion freezing (most important freezing process in mixed phase clouds (at T between
0°C and -38°C), e.g., Ansmann et al., 2008; de Boer et al. 2011; Westbrook and Illingworth,
2013)
Heike Wex, 16.3.2022, Virtual lecture series-Cloud and Precipitation Physics and Dynamics

5general introduction

cloudsscattering of lighthomogeneous
ice nucleation

T < -38°C
Bergeron-Findeisen
process
aggregationeven mineral dust
particles can be CCN!
heterogeneous
ice nucleation
Karydis et al.,2011
secondaryice

Hallett-Mossop
processformation
supercooled droplets
CCN activation

warm clouds (T > 0°C)

cloud base: RHw ≥ 100%

melting

precipitation
aerosol including CCN and INP(cloud condensation nuclei and ice nucleating particles)

adjusted from sketch
by Dennis Niedermeier

Heike Wex, 16.3.2022, Virtual lecture series-Cloud and Precipitation Physics and Dynamics

6general introduction

cloudsscattering of lighthomogeneous
ice nucleation

T < -38°C
Bergeron-Findeisen
process
aggregation

mixed phase clouds (-38°C < T < 0°C):- mainly immersion freezing
heterogeneous
ice nucleation

secondary ice
formation

Hallett-Mossop
process

supercooled droplets
CCN activation

warm clouds (T > 0°C)

cloud base: RHw ≥ 100%

melting

precipitation
aerosol including CCN and INP(cloud condensation nuclei and ice nucleating particles)

adjusted from sketch
by Dennis Niedermeier

Heike Wex, 16.3.2022, Virtual lecture series-Cloud and Precipitation Physics and Dynamics

6general introduction

cloudsice clouds (cirrus) (T < -38°C)- radiative effects- homogeneous freezing- different types of hetescattering of lightrogeneous freezing

homogeneous
ice nucleation

T < -38°C
Bergeron-Findeisen
process
aggregation

mixed phase clouds (-38°C < T < 0°C):- mainly immersion freezing- precipitation formation- radiative effects

heterogeneous
ice nucleation

secondary ice
formation

Hallett-Mossop
process

supercooled droplets
CCN activation

warm clouds (T > 0°C)

cloud base: RHw ≥ 100%

melting

precipitation
aerosol including CCN and INP(cloud condensation nuclei and ice nucleating particles)

adjusted from sketch
by Dennis Niedermeier

Heike Wex, 16.3.2022, Virtual lecture series-Cloud and Precipitation Physics and Dynamics

6general introduction

cloudsice clouds (cirrus) (T < -38°C)- radiative effects- homogeneous freezing- different types of hetescattering of lightrogeneous freezing

homogeneous
ice nucleation

INP

T < -38°C
Bergeron-Findeisen
process
aggregation

mixed phase clouds (-38°C < T < 0°C):- mainly immersion freezing- precipitation formation- radiative effects

heterogeneous
ice nucleation

secondary ice
formation

Hallett-Mossop
process

supercooled droplets
CCN activation

warm clouds (T > 0°C)

cloud base: RHw ≥ 100%

melting

precipitation
aerosol including CCN and INP(cloud condensation nuclei and ice nucleating particles)

adjusted from sketch
by Dennis Niedermeier

Heike Wex, 16.3.2022, Virtual lecture series-Cloud and Precipitation Physics and Dynamics

6general introduction

re-emergence of INP research:- review by Szyrmer & Zawadzki (1997) on „biogenic and anthropogenic sources“ of INP- increased activity in the field of INP starting ~ 2010
- newer reviews: Hoose & Möhler (2012); Murray et al. (2012); Coluzza et al. (2017); Kanji et al. (2017)

Heike Wex, 16.3.2022, Virtual lecture series-Cloud and Precipitation Physics and Dynamics

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Augus t
19
Jul y
10
June
10
Ma y
17
review by Szyrmer & Apri
Zawadzki(1997) on „biogenic
and anthropogenic sources“ of INPl20
Ma rch33
increased activity inFebruary
the field of INP starting
12 ~ 2010
Ja nuary
18
newer reviews: HooseTotal& Möhler (2012); Murray
et al. (2012); Coluzza et al. (2017); Kanji et al. (2017)187

general introduction

re-emergence of INP research:-

Table 2. Annual sum of publications
relevant to atmospheric ice nucleation
Year

Paper # - Annual Sum

2021
2020
2019
2018
2017
2016
2015
2014
2013
AnnualAverage

187
222
204
238
178
230
283
216
186

tables from Naruki Hiranuma, whopublishes a monthly summaryon new publications related to INP(nhiranuma@wtamu.edu)

216

Heike Wex, 16.3.2022, Virtual lecture series-Cloud and Precipitation Physics and Dynamics

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summarizing the general introduction
INP are- needed for ice nucleation in mixed phase clouds- important for cloud radiative effects and precipitation formation- very rare among atmospheric aerosol particles- immersion freezing is the most important process for ice nucleation in mixed
phase clouds

Heike Wex, 16.3.2022, Virtual lecture series-Cloud and Precipitation Physics and Dynamics

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basic knowledge

ice nucleation by mineral dust particles- surface sites, nicely demonstrated by
Kiselev et al. (2016)

Heike Wex, 16.3.2022, Virtual lecture series-Cloud and Precipitation Physics and Dynamics

9basic knowledge

ice nucleation by mineral dust particles- surface sites, nicely demonstrated by
Kiselev et al. (2016)
1000 nm- size dependence

700 nmHartmann et al. (2016)

300 nmkaolinite

frozen fraction: ficeHeike Wex, 16.3.2022, Virtual lecture series-Cloud and Precipitation Physics and Dynamics

10basic knowledge

ice nucleation by mineral dust particles- surface sites, nicely demonstrated by
Kiselev et al. (2016)- size dependence
Hartmann et al. (2016)

kaolinitesurface site density ns accounts for that (Niemand et al., 2012)
frozen fraction: ficeparticle surface area per droplet S

ns = - ln (1 - fice ) / S

Heike Wex, 16.3.2022, Virtual lecture series-Cloud and Precipitation Physics and Dynamics

10basic knowledge

ice nucleation by mineral dust particles- surface sites, nicely demonstrated by
Kiselev et al. (2016)- size dependence
Hartmann et al. (2016)- K-feldspar is the most ice active
mineralAtkinson et al. (2013)
Augustin-Bauditz et al. (2014)
Peckhaus et al. (2016)

Heike Wex, 16.3.2022, Virtual lecture series-Cloud and Precipitation Physics and Dynamics

10basic knowledge

ice nucleation by biological particles
bacteria

pollencell: 10 mm length, 2 mm width

ice nuc.: protein complexes
in the cell membrane

grain: 20 to 30 mm in diameter

fungal spores

spore: dimensions from 2 to10 mm

ice nuc.: polysaccharides but also proteins,can easily be washed off

Heike Wex, 16.3.2022, Virtual lecture series-Cloud and Precipitation Physics and Dynamics

11basic knowledge

ice nucleation by biological particles
bacteria

pollencell: 10 mm length, 2 mm width

ice nuc.: protein complexes
in the cell membrane

grain: 20 to 30 mm in diameter

fungal spores

spore: dimensions from 2 to10 mm

ice nuc.: polysaccharides but also proteins,can easily be washed off-> ice nucleation rates for single macromoleculesfrom bacteria,
pollenand fungal spores

Hartmann et al. (2013)

Augustin et al. (2013)

Pummer et al. (2015)

Heike Wex, 16.3.2022, Virtual lecture series-Cloud and Precipitation Physics and Dynamics

11basic knowledge

ice nucleation by biological particles

single macromolecules

Pummer et al. (2015)

Heike Wex, 16.3.2022, Virtual lecture series-Cloud and Precipitation Physics and Dynamics

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basic knowledge

testing for biogenic INP (proteins)
Hill et al. (2016)
soil dust

heating samples
to testfor proteinaceous INP

NINP

O’Sullivan et al. (2018)
UK airborne samples

Chen et al. (2021)
1
Heike Wex, 16.3.2022, Virtual lecture series-Cloud and Precipitation Physics and DynamicsBeijing dust storms

basic knowledge

laminar flow tube
LACIS

measuring INP in-situ
continuous flow
diffusion chambers

typically singe particle optical detection

CFDC, PINC, SPIN,
HINC, INCA, …

different operating principles, some can beboughtHartmann et al. (2011)

expansionchambers
PINE,
AIDA, …
Möhler et al. (2021)

Rogers et al. (1988)
Stetzer et al. (2008)
Garimella et al. (2016)

Heike Wex, 16.3.2022, Virtual lecture series-Cloud and Precipitation Physics and Dynamics

14basic knowledge

laminar flow tube
LACIS

measuring INP in-situ
continuous flow
diffusion chambers

typically singe particle optical detection

CFDC, PINC, SPIN,
HINC, INCA, …

different operating principles, some can beboughtadvantage:- high time resolution- closer to what happens in atmosphere

Hartmann et al. (2011)

expansionchambers
PINE,
AIDA, …
Möhler et al. (2021)

Rogers et al. (1988)
Stetzer et al. (2008)
Garimella et al. (2016)

disadvantage:- comparably high detection limit (low INP
concentrations cannot be detected)- typically more difficult to operate- large particles may need to be rejected at inlet

Heike Wex, 16.3.2022, Virtual lecture series-Cloud and Precipitation Physics and Dynamics

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measuring INP off-line
cold-stage and freezing array for suspensions(e.g., washed filters, suspensions of samples, rainor ocean water, … ; INDA also for filter punches)a large number of these instruments has started
to be operated in different groups

LINA ** Leipzig Ice Nucleation Array** Ice Nucleation Droplet Array

INDA **

V= 1 μL
in onedroplet,90 droplets

V=50 μL
in onedroplet,96 droplets

working cleanly:
Polen et al. (2018)

Barry et al. (2021)
droplets on a glass
slide, cooled by a
Peltier element
e.g., Budke & Koop
et al. (2015)
Heike Wex, 16.3.2022, Virtual lecture series-Cloud and Precipitation Physics and Dynamics

PCR-trays ina thermostat
Conen et al. (2012),
Hill et al. (2014)15

measuring INP off-line
cold-stage and freezing array for suspensions(e.g., washed filters, suspensions of samples, rainor ocean water, … ; INDA also for filter punches)a large number of these instruments has started
to be operated in different groups

LINA ** Leipzig Ice Nucleation Array** Ice Nucleation Droplet Array

INDA **

V= 1 μL
in onedroplet,90 droplets

V=50 μL
in onedroplet,96 droplets

advantage:- detection of lower INP concentrations- additional analysis possible
disadvantage:- contamination -> difficult to reach down to lowtemperatures (exception: pico-liter droplets, but
droplet production and optical detection much
more expensive)- long sampling times -> bad time resolution

droplets on a glass
slide, cooled by a
Peltier element
e.g., Budke & Koop
et al. (2015)

Heike Wex, 16.3.2022, Virtual lecture series-Cloud and Precipitation Physics and Dynamics

PCR-trays ina thermostat
Conen et al. (2012),
Hill et al. (2014)15

basic knowledge

evaluating
off-lineINP
data
cumulative distribution
1

fice

0.1

0.01

-25

-20

-15

-10

-5

T [°C]

fice-> fraction of frozen droplets from all droplets

Heike Wex, 16.3.2022, Virtual lecture series-Cloud and Precipitation Physics and Dynamics

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basic knowledge

evaluating
off-lineINP
data
cumulative distribution
1

Poisson distribution:

fice

0.1

 = - ln (1 - fice )( e.g., fice = 0.4 ->  = 0.51 )

0.01

-25

-20

-15
T [°C]

Vali (1971)

-10

-5



-> for us: average number of ice active entities per droplet

fice-> fraction of frozen droplets from all droplets

Heike Wex, 16.3.2022, Virtual lecture series-Cloud and Precipitation Physics and Dynamics

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basic knowledge

evaluating
off-lineINP
data
cumulative distribution
1
10

-2

fice

0.1

 = - ln (1 - fice )( e.g., fice = 0.4 ->  = 0.51 )0.01

NINP [1/L]

Poisson distribution:

10

-3

10

-4

-25

-25

-20

-15

-10

-5

Normalization:

-15

-20

-10

-5

T [°C]

T [°C]NINP =  / Vsample = - ln (1 - fice ) / Vsample
Vali (1971)
Heike Wex, 16.3.2022, Virtual lecture series-Cloud and Precipitation Physics and Dynamics

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basic knowledge

where to measure with which instrument

Cziczo et al. (2017)

Heike Wex, 16.3.2022, Virtual lecture series-Cloud and Precipitation Physics and Dynamics

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basic knowledge

concentrations of ice nucleating particles (NINP)
1000

atmospheric INP concentration [1/L]

Petters & Wright, (2015)

1

10-3

10-6
-35

temperature [°C]-10

Heike Wex, 16.3.2022, Virtual lecture series-Cloud and Precipitation Physics and Dynamics

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basic knowledge

concentrations of ice nucleating particles (NINP)
1000

atmospheric INP concentration [1/L]

Petters & Wright, (2015)

1

10-3

10-6
-35

temperature [°C]-10

Heike Wex, 16.3.2022, Virtual lecture series-Cloud and Precipitation Physics and Dynamics

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summarizing basic knowledge- in the atmosphere, mainly two main INP types contribute:
mineral dust particles and microorganisms- microorganisms have macromolecules causing the ice activity (proteins or polysaccarides)- they are very ice active, but VERY rare
- heat can destroy bio-INP (proteins)- mineral dust particles have ice active sites- they are ice active at lower temperatures but are more abundant, however, still rare
- K-feldspar is the most ice active mineral dust
- a multitude of instruments exist to measure INP in-situ or off-line; all with strength andweaknesses( topic of parameterization will be left out due to time limits -> additional backup slides )Heike Wex, 16.3.2022, Virtual lecture series-Cloud and Precipitation Physics and Dynamics

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upcoming results from recent field studies
Where do we have which INP concentrations?
Where do these INP come from?
31 publications from 2013 until 2022-> sources and occurrences

only few main messages

number of publications used6

mostly based on off-line methods &5mostly ground based measurements

4

3

2

1

TROPOS cloud group02013 2014 2015 2016 2017 2018 2019 2020 2021 2022

year

Heike Wex, 16.3.2022, Virtual lecture series-Cloud and Precipitation Physics and Dynamics

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results from recent field studies

highly ice active atmospheric INP often supermicron- Mason et al. (2016)- Creamean et al. (2018), Arctic

number fraction of INP > 1 mm

- Gong et al. (2020), Cabo Verde

Heike Wex, 16.3.2022, Virtual lecture series-Cloud and Precipitation Physics and Dynamics

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results from recent field studies

INP and anthropogenic pollution- Chen et al. (2018):
Beijing air pollution did not contribute INP (down to -25°C)-16°C

gray area:
Petters & Wright (2015)

Heike Wex, 16.3.2022, Virtual lecture series-Cloud and Precipitation Physics and Dynamics

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results from recent field studies

INP and anthropogenic pollution- Chen et al. (2018):
Beijing air pollution did not contribute INP (down to -25°C)

however, there is a clear increase in INP in
Beijing during dust events
Chen et al. (2021)-16°C

gray area:
Petters & Wright (2015)

Heike Wex, 16.3.2022, Virtual lecture series-Cloud and Precipitation Physics and Dynamics

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results from recent field studies

INP and anthropogenic pollution- Chen et al. (2018):
Beijing air pollution did not contribute INP (down to -25°C)- Tarn et al. (2018):
no increase in INP during a night with bonfires in the UK

Heike Wex, 16.3.2022, Virtual lecture series-Cloud and Precipitation Physics and Dynamics

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results from recent field studies

INP and anthropogenic pollution- Chen et al. (2018):
Beijing air pollution did not contribute INP (down to -25°C)- Tarn et al. (2018):
no increase in INP during a night with bonfires in the UK- Welti et al. (2020):
potential contribution of ship exhaust to INP only below -36 °C- Yadav et al. (2019)no contribution of local pollution to INP in Northern India- Tobo et al. (2020):
year round data-set in Tokyo, INP variations from long range
transported dust and biological INP

Heike Wex, 16.3.2022, Virtual lecture series-Cloud and Precipitation Physics and Dynamics

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results from recent field studies

INP and anthropogenic pollution- Chen et al. (2018):
Beijing air pollution did not contribute INP (down to -25°C)- Tarn et al. (2018):
no increase in INP during a night with bonfires in the UK- Welti et al. (2020):
potential contribution of ship exhaust to INP only below -36 °C- Yadav et al. (2019)no contribution of local pollution to INP in Northern India- Tobo et al. (2020):
year round data-set in Tokyo, INP variations from long range
transported dust and biological INP- Thomson et al. (2017):
ship emmission plumes in habor of Gothenburg, Sweden
showed increased INP concentrations
Heike Wex, 16.3.2022, Virtual lecture series-Cloud and Precipitation Physics and Dynamics

24results from recent field studies

INP in the Arctic- Creamean et al. (2018):
supermicron particles contribute strongly increased INP concentrations in May

Heike Wex, 16.3.2022, Virtual lecture series-Cloud and Precipitation Physics and Dynamics

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results from recent field studies

INP in the Arctic- Creamean et al. (2018):
supermicron particles contribute strongly increased INP concentrations in May- Wex et al. (2019):
high summertime INP concentrations at 4 Arctic stations,(Alert, Ny Alesund, Villum, Utqiagvik)

Utqiagvik

highest:
2013
Apr22
Apr03
May27
May31
2012
July16Aug12Aug18NINP [1/L]

10-2

10-3

10-4

10-5

lowest:
2012
Dec28
2013
Jan05
Jan18
Feb08
Feb15
Mar20

-20

-15

-10

T [°C]

Heike Wex, 16.3.2022, Virtual lecture series-Cloud and Precipitation Physics and Dynamics

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-5

0

results from recent field studies

INP in the Arctic- Creamean et al. (2018):
supermicron particles contribute strongly increased INP concentrations in May- Wex et al. (2019):
high summertime INP concentrations at 4 Arctic stations,(Alert, Ny Alesund, Villum, Utqiagvik), marine OR terrestrial sources

Utqiagvik

highest:
2013
Apr22
Apr03
May27
May31
2012
July16Aug12Aug18NINP [1/L]

10-2

10-3

10-4

10-5

lowest:
2012
Dec28
2013
Jan05
Jan18
Feb08
Feb15
Mar20

-20

-15

-10

T [°C]

Heike Wex, 16.3.2022, Virtual lecture series-Cloud and Precipitation Physics and Dynamics

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-5

0

results from recent field studies

INP in the Arctic- Creamean et al. (2018):
supermicron particles contribute strongly increased INP concentrations in May- Wex et al. (2019):
high summertime INP concentrations at 4 Arctic stations; marine OR terrestrial sources- Hartmann et al. (2019) & Schrod et al. (2020)
no increase in INP from ice cores (some hundred years back, going up to 1990)(the latter: maybe a small increase after 1960,
due to land-use change)

https://archaeologynewsnetwork.blogspot.com/2015/09/ice-sample-from-greenland-and-russia.html

Heike Wex, 16.3.2022, Virtual lecture series-Cloud and Precipitation Physics and Dynamics

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results from recent field studies

INP in the Arctic- Creamean et al. (2018):
supermicron particles contribute strongly increased INP concentrations in May- Wex et al. (2019):
high summertime INP concentrations at 4 Arctic stations; marine OR terrestrial sources- Hartmann et al. (2019) & Schrod et al. (2020)
no increase in INP from ice cores (some hundred years back, going up to 1990)(the latter: maybe a small increase after 1960,
due to land-use change)-> antropogenic pollution does not contribute INP-> BUT: future changes due to Arctic Amplification may
change INP concentrations and therewith clouds

https://archaeologynewsnetwork.blogspot.com/2015/09/ice-sample-from-greenland-and-russia.html

Heike Wex, 16.3.2022, Virtual lecture series-Cloud and Precipitation Physics and Dynamics

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results from recent field studies

INP in the Arctic - sources- possible terrestrial sources:
Santl-Temkiv et al. (2019)
Si et al. (2019)
Tobo et al (2019)
Sanchez-Marroquin et al. (2020)– Villum, northern Greenland: local dust source with biogenic contribution– Alert, Canada: INP @ -25°C -> long range dust transport from Gobi desert– Svalbard: local dust source, glacial outwash, connected to organic material– Iceland: local dust source

Heike Wex, 16.3.2022, Virtual lecture series-Cloud and Precipitation Physics and Dynamics

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results from recent field studies

INP in the Arctic - sources- possible terrestrial sources:
Santl-Temkiv et al. (2019)
Si et al. (2019)
Tobo et al (2019)
Sanchez-Marroquin et al. (2020)– Villum, northern Greenland: local dust source with biogenic contribution– Alert, Canada: INP @ -25°C -> long range dust transport from Gobi desert– Svalbard: local dust source, glacial outwash, connected to organic material– Iceland: local dust source-> there are Arctic dust sources which may beconnected to biogenic INP-> biogenic INP may be emitted from the terrestrial
biosphere-> long range transport may also contribute INPHeike Wex, 16.3.2022, Virtual lecture series-Cloud and Precipitation Physics and Dynamics

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results from recent field studies

INP in the Arctic - sources- possible marine sources:
Irish et al. (2017)
Hartmann et al. (2020)– INP in Arctic ocean, particularly close to melting sea ice– airborne sampling over ice in March, INP from open polynyas

Heike Wex, 16.3.2022, Virtual lecture series-Cloud and Precipitation Physics and Dynamics

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results from recent field studies

INP in the Arctic - sources- possible marine sources:
Irish et al. (2017)
Hartmann et al. (2020)
Porter et al. (2022)– INP in Arctic ocean, particularly close to melting sea ice– airborne sampling over ice in March, INP from open polynyas– highly varying INP concentrations at theNorth Pole, up to very high values-> marine biogenic
sources may also
contribute INPHeike Wex, 16.3.2022, Virtual lecture series-Cloud and Precipitation Physics and Dynamics

1results from recent field studies

INP in the Arctic - sources- possible marine sources:
Irish et al. (2017)
Hartmann et al. (2020)
Porter et al. (2022)– INP in Arctic ocean, particularly close to melting sea ice– airborne sampling over ice in March, INP from open polynyas– highly varying INP concentrations at theNorth Pole, up to very high values

Knackstedt et al. (2018):
rivers contain INP fromterrestrial sources-> marine (?) biogenic
sources may also
contribute INPHeike Wex, 16.3.2022, Virtual lecture series-Cloud and Precipitation Physics and Dynamics

1results from recent field studies

but- Gong et al. (2020) at Cabo Verde and Hartmann et al. (2021) during ship cruise in the Arctic
INP concentrations in the ocean water (bulk and surface microlayer (SML) are orders of magnitude too low to explain
related atmospheric INP concentrations, UNLESS there is strong enrichment during bubble burstingmeasured atmospheric INP concentration

INP concentration expected from bubble bursting,based on INP concentrations in sea water

Heike Wex, 16.3.2022, Virtual lecture series-Cloud and Precipitation Physics and Dynamics

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results from recent field studies

INP in remote oceanic regions / Southern Ocean- McCluskey et al. (2018a,b):
very low INP concentrations in the Southern Ocean and the clean North-East Atlantic

Heike Wex, 16.3.2022, Virtual lecture series-Cloud and Precipitation Physics and Dynamics

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results from recent field studies

INP in remote regions / Southern Ocean- McCluskey et al. (2018a,b):
very low INP concentrations in the Southern Ocean and the clean North-East Atlantic- Welti et al. (2020):
INP concentrations from ship based measurements: lower by 1 order of magnitude for marine, compared to continental,
Southern Ocean even one order of magnitude lower- Zeppenfeld et al. (2021) (on and around Western Antarctic Peninsula)and Tatzelt et al. (2022) (Antarctic circumnavigation):
also very low INP concentrations in the Southern Ocean-15°C

Heike Wex, 16.3.2022, Virtual lecture series-Cloud and Precipitation Physics and Dynamics

1results from recent field studies

INP in remote regions / Southern Ocean- McCluskey et al. (2018a,b):
very low INP concentrations in the Southern Ocean and the clean North-East Atlantic- Welti et al. (2020):
INP concentrations from ship based measurements: lower by 1 order of magnitude for marine, compared to continental,
Southern Ocean even one order of magnitude lower- Zeppenfeld et al. (2021) (on and around Western Antarctic Peninsula)and Tatzelt et al. (2022) (Antarctic circumnavigation):
also very low INP concentrations in the Southern Ocean

fits to high fractions of supercooled liquid
droplets in clouds over the Southern Ocean
observed from satellite
Choi et al. (2010), Zhang et al., (2018)-15°C

Heike Wex, 16.3.2022, Virtual lecture series-Cloud and Precipitation Physics and Dynamics

1results from recent field studies

long term studies- Schneider et al. (2021):
boreal forest in Finnland, seasonal INP cycle linked to the prevalence of biogenic aerosol particles-> parameterization wrt. temperature

Heike Wex, 16.3.2022, Virtual lecture series-Cloud and Precipitation Physics and Dynamics

32

results from recent field studies- Schrod et al. (2020):

more long term studies

4 stations: Arctic (Svalbard), central Europe (Germany), Caribbean (Martinique) and Amazon (Brazil), data at -20°C and -25°C
short-term variability overwhelms all long-term trends and/or seasonality
Amazon mostly unaffected by biomass burningseasonno anthropogenic influence in Europe or Arctic
Carribean affected by long range dust transport

Heike Wex, 16.3.2022, Virtual lecture series-Cloud and Precipitation Physics and Dynamics

1results from recent field studies

more long term studies- Testa et al. (2021):
north central Argentina, 7 month (austral spring to mid fall), no seasonal cycle
heat labile INPs dominated at -5 to -20°C
non-heat-labile organic INPs (H2O2-treatment) dominated from -20 to -28°C,
their ratio to mineral dust was constant-> likely regional INP from arable topsoil

bio INP peaked during rain
& high relative himidity

Heike Wex, 16.3.2022, Virtual lecture series-Cloud and Precipitation Physics and Dynamics

34

results from recent field studies

more long term studies- Gong et al. (2022):

southern Chile (600m high, 8km west of Punta Arenas),
11 month (May to March), no seasonal cycle,
suprisingly high INP concentrations
high fraction of heat liable (biogenic) INP down to -16°C
precipitation enhances INP concentrations-> see also Huffman et al. (2013)

Heike Wex, 16.3.2022, Virtual lecture series-Cloud and Precipitation Physics and Dynamics

35

summary for results from recent field studies- a large number of atmospheric INP is supermicron in size (down to -25°C)- no INP from anthropogenic pollution for temperatures typical for mixed phase clouds- annual cycle for highly ice active (biogenic) INP in some locations (Arctic, Finnish boreal forest)
but not everywhere (North Central Argentina, southern Chile)and also no annual cycle at -20°C and -25°C- summertime Arctic can have INP concentrations as observed over mid-latitude continents- remote marine regions (Southern Ocean, clean North West Atlantic) have low INP concentrations- INP from sea spray production can not explain atmospheric INP concentrations in marine areas
without INP enrichment during bubble bursting process- enhanced INP concentrations over continents, maybe connected to precipitation
Heike Wex, 16.3.2022, Virtual lecture series-Cloud and Precipitation Physics and Dynamics

36

Heike Wex, 16.3.2022, Virtual lecture series-Cloud and Precipitation Physics and Dynamics

concentrations of ice nucleating particles (NINP)
Petters & Wright,
GRL (2015)

Fletcher (1962):- overestimation
at lower
temperatures- does not
capture observed
variations

parameterizations for NINP
DeMott et al.,PNAS (2010)

parameterizations for NINP
DeMott et al.,PNAS (2010)

Heike Wex, 20.9.2018 @ DFG SPP 1294 “HALO” Topical workshop

parameterizations for NINP
DeMott et al.,PNAS (2010)

by now, there are anumber of updated
versions of this fit, e.g.,
Tobo et al. (2013),
DeMott et al. (2015)

Heike Wex, 20.9.2018 @ DFG SPP 1294 “HALO” Topical workshop

parameterizations for NINP
Niemand et al.,J. Atmos. Sci. (2012):- ice nucleation active
surface site density ns- dependent on
available surface
area of mineral dustbut:

* is only valid for small fice , asstated in the paper!

f= ice
Sdroplet*that comes from using only the first term of a Taylor series expansion-> full equation: ns = - ln (1 - fice ) / Sdroplet

parameterizations for NINP
Niemand et al.,J. Atmos. Sci. (2012):- ice nucleation active
surface site density ns- dependent on
available surface
area of mineral dust

parameterizations for NINP
Wilson et al.,Nature, (2015)

Atkinson et al.,Nature, (2013)

parameterizations for NINP
Wilson et al.,Nature, (2015)

Atkinson et al.,Nature, (2013)

parameterizations for NINP
Wilson et al.,Nature, (2015)

developed further:
Vergara-Temprado etal., ACP (2017)-> discrepancies
possibly due tomissing contributions
from terrestrial
biosphere

Heike Wex, 16.3.2022, Virtual lecture series-Cloud and Precipitation Physics and Dynamics

1

In the temperature range between 0 and -38°C, ice nucleation in atmospheric cloud droplets has tobe aided by a catalyst, which is provided by one kind of atmospheric aerosol particles, INP (icenucleating particles). Therefore, INP are important for mixed phase clouds, but also for some ice
formation in cirrus clouds. And the ice formation, in turn, is important for cloud radiative effects,
precipitation formation and cloud lifetime.
INP comprise different types of particles, more specifically biological and mineral dust particles. They
are very rare in general, but still occur in vastly varying concentrations, depending on factors as
location on Earth, season and temperature. Intensive laboratory research on INP was done in the past
decade, while now the focus has shifted at understanding atmospheric INP based on atmosphericmeasurements. This presentation will provide some basic understanding of ice nucleation andmeasurements principles, will summarize the main findings from laboratory studies and then give an
overview of the newest understanding gained from atmospheric measurements in the past years.
Due to the vastness of the topic, it is thought as spark that may kindle curiosity and further own
research in this important topic.

laminar flow tube
LACIS

measuring INP in-situ

Heike Wex, 16.3.2022, Virtual lecture series-Cloud and Precipitation Physics and Dynamics

1measuring INP in-situ

opticaldetection

Heike Wex, 16.3.2022, Virtual lecture series-Cloud and Precipitation Physics and Dynamics

warm wall

aerosol laminar

ice

ice

continuous flow
diffusion chambers

cold walllaminar flow tube
LACIS

evaporation
section1

laminar flow tube
LACIS

measuring INP in-situ

30
20
10

0.02
0.04
0.06
0.08

0.1

1.14
1.12
1.1
1.08
1.06
1.04
1.02
1

opticaldetection-40 -38 -36 -34 -32 -30
Garimella
et al.,
temperature[°C]
Heike Wex, 16.3.2022, Virtual
lecture series-Cloudand Precipitation
Physics
and2016
Dynamics

warm wallcold wall40

aerosol laminar

50

supersat. wrt. ice

vapor pressure [Pa]flow velocity [m/s]ice

distance to cold wall [mm]
0
2
4
6
8
10

ice

continuous flow
diffusion chambers

evaporation
section1

courtesy of Sarah Grawe,adapted from Stetzer et al. (2008)

laminar flow tube
LACIS

measuring INP in-situ
continuous flow
diffusion chambers
CFDC, PINC, SPIN,
HINC, INCA, …

Heike Wex, 16.3.2022, Virtual lecture series-Cloud and Precipitation Physics and Dynamics

1laminar flow tube
LACIS

measuring INP in-situ
continuous flow
diffusion chambers
CFDC, PINC, SPIN,
HINC, INCA, …

expansionchambers

Heike Wex, 16.3.2022, Virtual lecture series-Cloud and Precipitation Physics and Dynamics

1